Apparatus for producing a continuous tubular article



May 25;"1965 'R. *P. PLOURDE APPARATUS FOR PRODUCING A CONTINUOUSTUBULAR ARTICLE Original Filed Aug. 9. 1961 ROGER I? PLOURDE BY I; I);

ATTORNEY United States Patent 3,184,793 APPARATUS FGR PRGDUiZlNG ACQNTENUQUS TUBULAR ARTIfiLE Roger 1. Plourde, 68 Maple St, Paxton, Mass.Continuation of application Ser. No. 130,420, Aug. 9, 1961. Thisapplication Apr. 3, 1%4, Ser. No. 358,144 1 Claim. (ill. 18-14) This ina continuation of patent application Serial Number 130,420, filed August9, 1961, now abandoned.

This invention relates to apparatus for producing continuous tubulararticle and, more particularly, to apparatus arranged to produce acorrugated or similar nonextrudable article from a heat-softenedseamless tube of plastic.

In the past, there has been considerable demand for a corrugated orflexible hose formed of plastic of sufiicient thickness and hardness tobe self-supporting and to withstand internal pressures. Such hose wouldbe useful, for instance, in vacuum cleaners where the internal pressurewould be a suction, or in automobile cooling system hoses where thepressure is a positive one. While it has been possible to form suchhoses in small lengths by a batch process using a mandrel or by blowmolding, it has been impossible to do so continuously. The hose at thepresent time is formed on a mandrel by winding a soft plastic tapearound a wire coiled on the mandrel, the wire providing the physicalsupport for the hose. The hose which is formed in this manner isnecessarily formed of thin-walled, flexible plastic of very low strengthwhich is easily perforated and torn. The presence of the wire is ahandicap in some cases, also. Although the batch process of producingthe corrugated tube is adequate for some purposes, generally speaking,it is expensive and it is not possible to use the tube thus formed inautomatic machinery which use a continuous length of material and alsothe length is definitely limited. These and other difiicultiesexperienced with the prior art apparatus have been obviated in a novelmanner by the present invention.

It is, therefore, an outstanding object of the invention to provide anapparatus for producing a continuous tubular article from aheat-softened seamless tube of plastic.

Another object of this invention is the provision of an apparatus forproducing corrugated plastic tube whose wall thickness and strength issufficient to support appreciable pressure and still be capable ofaccepting sharp radius bends; the corrugations also enable a tubing tobe produced from a rigid material which, without corrugations, would bea stiff tube or pipe but, with the corrugations, is capable of beingbent through the creation of bending moments.

A further object of the present invention is the provision of anapparatus for continuously producing corrugated tubing formed of plasticwhich apparatus is simple in construction, inexpensive to manufacture,and which is capable of a long life of useful service.

It is another object of the instant invention to provide an apparatusfor producing corrugated plastic tubing continuously by a vacuum moldingprocess.

It is a further object of the invention to provide an appartus forproducing a non-extrudable continuous article, such as corrugatedtubing, by a vacuum molding process whereby a thin wall of considerablestrength is obtained.

A still further object of this invention is the provision of anappaartus using a suction molding process for producing intermittent,thin-walled, continuously-linked articles of plastic.

It is a still further object of the present invention to provide anapparatus for producing a corrugated tube from thermoplastic material bya combination of extrusion and vacuum molding.

Another object of the invention is the provision of apparatus forforming corrugated plastic tube, wherein one is given freedom of design,of material, of color, and of configuration of the corrugations.

With these and other objects in view, as will be apparent to thoseskilled in the art, the invention resides in the combination of partsset forth in the specification and covered by the claim appended hereto.

The character of the invention, however, may be best understood byreference to certain of its structural forms as illustrated by theaccompanying drawings in which:

FIG. 1 is an elevational view partly in section of an apparatusembodying the principles of the present invention;

FIG. 2 is a horizontal sectional view of the invention taken on the lineIIII of FIG. 1; and

FIG. 3 is a vertical sectional View of the apparatus taken on the lineIIIIII of FIG. 2.

Referring first to FIG. 1, which best shows the general features of theinvention, the apparatus, indicated by the reference numeral 10, isshown as consisting of an extruder 11 of the cross-head type and acorrugating apparatus 12. The extruder is provided with a housing 13having a horizontal bore 14 in which resides a material-feeding screw15, which is rotatable in the usual manner to force plastic through thebore 14. The bore 14 is provided at the end shown in the drawing with a'rightangle bore 16 which opens on the downward side of the housing andwhich is provided with a die 17. The die is provided with a tapered bore18 having its narrow end at the exterior portion of the die and facingdownwardly. Within the bore 16 lies a tapered vertical pin 19 whichterminates in the same horizontal plane with the bottom surface of thedie 17 and which is exactly concentric with the bore 18. The pin and thebore, therefore, define an annular tapered passage 21 through which theplastic is extruded. In the drawing is shown a tube 22 which has beenformed by the extruder 11 and which is formed of a thermoplasticmaterial. As is evident in the drawing, the tube 22 is a straightcylindrical tube in the portion between the extruder 11 and theapparatus 12 and this is known in the art as the parison 23. The portionof the tube 22 lying below the apparatus 12 is the finished product andis a corrugated tube 24.

Referring now to the corrugating apparatus 12, it can be seen that itconsists generally of two discs 25 and 26. The disc 25 is mounted forrotation on a shaft 27. To this shaft is keyed a gear 28 which mesheswith a similar gear 29 fastened to a shaft 31 on which the disc 26 isalso mounted. One of the shafts 2'7 and 31 is connected to a drivingmeans (not shown), so that the discs 25 and 26 may be driven at a speedcommensurate with the formation of the parison 23 by the extruder 11.The discs 25 and 26 are adapted to rotate in opposite senses so thattheir mating surfaces, which are tangential just below the passage 21,move at the same speed and in the same direction. The peripheries of thediscs are formed with large semi-circular grooves; the disc 25 isprovided with such a groove 32, while the disc 26 is provided with agroove 33. The groove 32 is formed in what would otherwise be thecylindrical edge of the disc and occupies only part of the disc edgesurface, thus leaving cylindrical surfaces 34 and 35 which aretangential with similar surfaces 36 and 37 which remain on thecylindrical edge of the disc 26 after the groove 33 is formed. Thesurface 34 and the surface 36 are tangential at a point midway betweenthe axles 2'7 and 31, while the surfaces 35 and 37 are similarlytangential. The grooves 32 and 33 form a perfect circle in theintermediate portion which, as is best shown in FIG. 2, contains thetube 22. Now, the groove 32, in addition to being generallysemi-circular, is also formed with lesser indentations. The groove isformed with alternate annular ridges 3S and pockets or grooves 39. Theannular ridges and grooves are trans verse of the major axis of thegroove 32. Similarly, the groove 33, is formed with ridges 41 andgrooves 42. The ridges and grooves on the respective discs 25 and 26 areequal in size and shape and when the discs rotate each groove of onedisc is matched by an exactly similar groove of the other disc;similarly, each ridge of one disc finds an exactly matching andcoincidental ridge on the other disc. Each one of the grooves 39 and 42of the discs 25 and 26, respectively, is provided with a number ofpassages or openings 43. These openings extend radially into the discand each of the series of openings in a given groove intersects apassage 44 which extends to one side of the disc parallel to the shaft.Pressed against the side of the disc 25 upon which all of the passages44 open is a comutator 45, while a similar commutator 46 is pressedagainst the side of the disc. 26. The commutator 45 is connected by apassage 47 to a source of suction (not shown), while the commutator 46is similarly connected by a-passage 48to the same source. Thecommutators, incidentally, are fixed in space on supports 49 and 51 anddo not rotate with the discs 25 and 26. The surface of the commutator 45which engages the radial surface of the disc 25. is provided with apocket 52 which is large enough to cover approximately two of thepassages 44 at any given time audit is located so that half of thepocket is above the line joining the shafts 27 and Bland half is belowthat line. Similarly, the commutator 46 is provided with a pocket 53.

Extending through the pin 19 is a thin vertical bore 54 through whichpasses a tube 55 whose lower end extends well. below the top level ofthe discs 25 and 26 and lies within the tube 22 as it is being extruded.The upper end of the tube 55 is connected to a source of slight positiveair pressure (not shown).

The operation of the apparatus will now be readily understood in view ofthe above. description. The plastic material is fed into the extruder 11and is forced along the bore 14 by the screw 15. The material is forceddown the bore 16 around the pin 19 and eventually passes through the die17. The tapered conformation of the passage 21 between the pin 19 andthe surface of the die bore 18 forms the parison 23 of the tube 22. Thisparison is still thermoplastic because of the heat furnished to theplastic by the heating means 2% embedded in the housing 13 of theextruder. The apparatus 12 is mounted as close to the extruder 11 as isphysically possible so that the parison 23 immediately moves between thediscs 25 and 26. As it moves downwardly, it is engaged by the grooves 32and 33 whose surfaces move because of the rotation of the discs 25 and26 in a downward direction at the same speed as the tube is extruded. Asthe parison 23 moves downwardly between the discs it is embraced in ageneral manner by the grooves 32 and 33. As

the tube 22 passes through the tangent point on a horizontal linejoining the shafts 2'7 and 31, however, it is definitely formed by theridges 38 and 41 of the discs 25:

and 26, respectively. These ridges form indentations on the tube whichextend completely around the tube, while the tube has a tendency to moveoutwardly and form ridges in the grooves 39 and 42. Now, referring tothe openings 43 in the grooves, it can be seen that, as the discsrotate, the passages 44 of a given set of openings eventually pass intothe pockets 52 and 53 of the commutators 45 and 46, respectively. Thesuction in the pockets is carried through to the openings, so that theopenings, which in general lie between the shafts 27 and 31, areprovided:

with suction, but none of the other openings are so provided. This meansthat the tube as it passes through the area between the drive shafts issucked into the grooves 39 of the disc 25.and the grooves 42 of the disc26. The outward bulge formed from the tube material is exactly annularand conforms to the shape of the grooves on the disc. Preferably, thediameter'of the tube 22 would be selected so thatthe pitch line of theformed surfaces in the grooves 32 and 33 of the discs is coincidentalwith the surface of the tube; generally speaking, then, as much materialis pressed inwardly by the ridges as would be sucked outwardly by thegrooves. The result is the emergence of the corrugated tube 24 from theapparatus 12. The corrugated tube thus formed may be cooled, coiled, orotherwise treated so that it will retain its form permanently. It iscontemplated, for instance, that the discs 25 and 26 may be cooled bypassing through pans of liquid 56 and 57 or the like.

It will be understood that, although in the preferred embodiment thegrooves and ridges in the discs are shown as being smoothlyformed ofgenerally circular cross-section and of annular form, they may be squarein conformation to form square-sided corrugations on the tube 24. Thesquare shape may, under the teaching of the present invention, involve asquare, configuration either when a section is taken parallel to theaxis or when it is taken at a right angle to the axis; the former may,for instance, resemble a square thread and the 0 latter may resemble aseries of boxes joinedby a small tube. Other variations of theconformations of the corrugationsand shapes of the tube 24 will suggestthemselves readily in view of the presentinvention.

It is obvious that minor changes may be made in the form andconstruction of the-invention without departing from the material spiritthereof; it is not, however, desired to confine the invention to theexact form herein shown and described, but it is desired to include allsuch as properlycome withinthe scope claimed.

The invention having been thus, described, what is claimed as new anddesired to secure by Letters Patent is:

Apparatus for producing a continuous corrugated tubular article from arecently-formed seamless tube of plas-. tic, comprising an extruder forforming the tube so that it emerges in a downward direction, at leasttwo rotary dies residing below the extruder on opposite sides of thetube as it emerges from the extruder, the dies being disclilre in formand being mountedfor rotation on generally horizontal parallel axes withtheir peripheries generally tangential, said peripheries being, formedwith smooth continuous grooves having cooperating forming surfacesconsisting of alternate annular ridgesand grooves lying in opposition toeach other, means for rotating the dies about their axes so that thesaid surfaces move at the same linear'speed as the tube, passagesopening on the said surfaces, the passages extending away from thesurfaces, said passages terminating with openings at the lateral surfaceof said discs, said openings positioned to form an annular ring,commutator means as a manifoldfor applying suction to. the passagesduring a forming portion of the movement of the dies, and means toprovide a slight positive pressure in the tube above the dies as itemerges from the extruder to cause the tube to form a seal with thesurface of the die.

References Cited by the Examiner UNITED STATES PATENTS 1,606,270 11/26Stratford.

2,497,212 2/50 Donofrio 18-21 X 2,545,300 3/51 Nixon 18-14 X 2,760,228.8/56 Verges 1814 X 2,866,230 12/58 Holte 18-19 2,945,261 7/ 60 Aykanianet a1. 18-12 X WILLIAM J. STEPHENSON, Primary Examiner.

MICHAEL V. BRINDISI, Examiner.

